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My Firefox doesn't play music either, and breaks some of the symbols used on the replay buttons. My IE plays music but I think it cuts out Pokemon cries, which I mainly use to know when I need to go back and pay attention to the match. So far I've found the game works best in Chrome?
http://pokemonshowdown.com/replay/doublescustomgamedev5941146
Ran into the Zoroark illusion glitch poster described, though what I saw on my screen was not what showed up in the replay. I had a perfectly playable game; my opponent, on the other hand, could not select my ZoroarkMienshao after...